Method of treating liquid insulated transformers



Patented Apr. 26, I

'UNITED STATES PATENT oFFi c'E.

EMIL STENKVIST, 0F LUDVIKA, SWEDEN, ASSIGNOIR TO ALLMANNA SVENSKA ELEK- TRISKA AKTIEBOLAGET, OF VASTERAS, SWEDEN, A CORPORATION OF SWEDEN.

ME THOD OF TREATING LIQUID INSULATED TRANSFORMERS.

N'o DrawHgQ- Application filed June 26, 1926, Serial No. 118,858 and in Sweden July 4 1925.

In transformers intended to operate with their windings immersed in an insulating and cooling liquid, it :is of utmost importance that the insulation is free from moisn tare to the highest possible degree before the immersion in the liquid. The drying processnecessary for this urpose, which preferably should be assiste by vacuum as well as by an appropriate heating, is rather circumstantialand must be performed with care and thoughtfulness b ersonsskilled in the art, if the result shall e satisfactory. I It is frequently not possible to perform the final filling with the insulating liquid immediately after thedrying operation.

Particularly in the'case of large transform-f ers it may with respect to their handling, transport and erection be found necessary to postpone the filling until a moment just before the taking into use of the transformer, which often may occur several months after the time which is most suitable for the dryin operation.

The method employed according to the present invention in completing transformers adapted for liquid insulation consists in filling their receptacle immediately after the drying of the transformer (after which liquid may have been temporarily filled in during testing or the like) with dry air or other gas under 'a pressure slightly higher than that of the atmosphere so as to prevent the external, moist air from entering the receptacle. A moisture-absorbing material,

for instance chloride of calcium, may preferably be introduced in the receptacle, and the latter may be in communication, through a reduction valve, with a vessel containing highly compressed air for replacing the loss through leakage. The enclosed, dry air is expelled immediately before the introducwith a dry gas under a pressure slightly higher than that of theatmosphere for storing or transport, expelling the gas and introducing liquid after storing or transport.

In testimony whereof I have signed my name to this specification.

EMIL STENKVIST. 

